The present invention relates to a rearview mirror for a vehicle which is extendable toward or away from the vehicle laterally to selectively provide different viewing positions as desired, for example when the vehicle is towing a trailer or the like.
It is known to provide vehicles with extendable rearview mirrors which extend selectively from the vehicle body along a support arm which extends laterally from the body of the vehicle. This type of extendable mirror is shown for example in U.S. Pat. No. 5,572,376 issued to Pace. The Pace mirror further includes a rack gear drive and a flexible boot which provides a cover between the vehicle and the motor housing to protect portions of the apparatus from exposure. A problem with this prior art device, however, is that the slidable components of the sub-assembly and support arm produce wear of the parts, thus creating undesirable movement in the slide assembly which produces excessive vibration in the mirror assembly resulting in poor vision through the mirror. It is known to use plate springs such as shown in the above-captioned U.S. patent to Pace to take up clearances between slide components of the extension arm mechanism however, because of the limited space between these parts, the practical use of this type of spring provides a spring force which is relatively weak in relation to the reaction forces created by the mass of the mirror sub-components.
Another extendable rearview mirror for a vehicle is disclosed in U.S. Pat. No. 6,116,743 issued to Hock. The mirror assembly of the Hock device includes a bracket which is slidable around a support arm and includes internal spring means for taking up the gap between the outer surface of the support arm and the inner surface of the bracket. This device is a complex assembly of many small parts including screws and other fasteners. U.S. Pat. No. 5,969,860 issued to Whitehead shows an extendable mirror which slides along longitudinal rails located on the outside of the mirror housing. Hence the rails are not protected from the adverse elements of the weather.
There is therefore a need in the art for an extensible rearview mirror support mechanism which is resistant to wear and which remains extremely stable and vibration-resistant throughout the entire stroke of its motion. It is further desired to provide a mechanism which is easily assembled to allow high volume manufacturing. For yet further economy of manufacture there is a need to provide a xe2x80x9cno-tool assemblyxe2x80x9d of parts.
In order to solve the needs in the art explained above, the present invention provides an extendable rearview mirror for a vehicle which provides a spring-clamped slide mechanism that ensures a zero tolerance fit between sliding components to avoid vibration. It further includes bearing members between the sliding components to reduce friction and provide a consistent reaction force to ensure smooth operation of the actuator mechanism. This type of mirror is particularly useful in situations where the vehicle is towing something behind it and enhanced rearward vision is provided by positioning the rearview mirror to its fully-extended position.
The superior functional characteristics of the present invention are provided by a unique support bar clamp mechanism which slidably affixes the rearview mirror housing and other components of the rearview mirror assembly to the support arm. The sliding movement is achieved with accurate slidable engagement of the mirror assembly along the support arm through the full extent of its longitudinal movement. This structure includes unique upper and lower V-shaped guide rails which face opposing V-shaped guide rails on the mounting bracket assembly. Rod-like bearing means are interposed between the bracket guide rails and the support arm guide rails to engage the mounting bracket and the support arm against movement in any direction except along the longitudinal axis of the support arm.
To achieve a sufficient amount of clamp force, the bracket assembly includes a cantilever clamp jaw which also includes the lower bracket guide rail. The clamp jaw is pivotal about a fulcrum and is biased toward clamping engagement with the support arm by spring means which is operative between a mirror sub-assembly mounting bracket and the lever arm of the clamp jaw which extends to the opposite side of the mounting bracket. Because of the shape of modern rearview mirror housings that is dictated by aesthetic considerations, there is a large void in the housing behind the mirror assembly mounting bracket. Since the spring means of the present invention is behind the bracket and positioned in this void, a single, large spring with a high spring force can be used. This high spring force provided by the present invention contributes significantly to the superior rigidity of the present design compared to the prior art. Support arm clamp force may be further increased by the mechanical leverage provided by the clamp jaw lever arm.
In one embodiment of the invention the bearing rods are composed of an ablatable material which leaves deposits on the support arm guide rails as it is used. These material deposits act as a filler to smooth over surface irregularities of the guide rails which may be present if inexpensive casting methods are used to form the rails. In this way, the respective bearing surfaces are increased in area as the bearings xe2x80x9cwear inxe2x80x9d. This occurs rapidly since the unit surface pressure between the bearing material and the guide rails is initially very high due to the very small point of contact between the cylindrical outer surface of the rod and the flat surfaces of the V-shaped rails. When the slide mechanism is operated, the material of the bearing rods is quickly removed from the rods and deposited along the surface of the support arm rails until a point of equilibrium is reached between the surface friction and the increase in bearing surface area. Once this wear-in point is reached, a consistent and low coefficient of surface friction is maintained.
More specifically, the applicants have invented an extendable rearview mirror assembly for a vehicle which includes a rotatable support arm for attachment to a vehicle body. A mirror assembly is mounted on the support arm and includes a bracket and a surrounding housing affixed thereto. A mirror sub-assembly including a mirror glass, support plate, and motor-driven positioning means is affixed to a first side of the bracket and lies within the housing. The assembly includes clamp means with jaws on the bracket for slidably affixing the bracket to the support arm. A first clamp jaw is adjacent the top of the housing and stationary with respect to the bracket and engages a first guide rail located along a top of the support arm. A second movable clamp jaw is adjacent the bottom of the housing and includes pivot means to forceably engage a second guide rail located along a bottom of the support arm. The first and second jaws define a substantially vertical clamping plane between them which lies along the first side of the bracket. The mirror assembly also includes a first bearing means interposed between the first jaw and first guide rail and a second bearing means interposed between the second jaw and the second guide rail. Both bearing means are elongate, rod-shaped members composed of solid PFTE, a substantially ablatable material, such that initial operation of the slide mechanism causes the bearing means to deposit friction-reducing material upon the surfaces of the guide rails. The first and second jaws each include a guide rail and face opposite their respective support arm guide rails. All guide rails further include surfaces which have a V-shaped cross-section. The movable clamp jaw includes force-applying spring means urging the second jaw in a direction of clamping and is movable to a point of release where the bracket is laterally releasable from the support arm. The second clamp jaw moves by way of a lever arm having a first end which engages the coil-type compression spring means and extends to an opposite side of the bracket. The bracket has a fulcrum about which the lever arm pivots. The fulcrum is on a bottom support plate of the bracket which holds the spring and the second jaw in their operative positions solely by the co-mutual compression of engaged parts. The spring operates between the end of the lever arm and an abutment both being located on the opposite side of the bracket. The aggregate center of mass of all components is adjacent the plane of clamping.
The assembly also comprises a support arm having a mounting bracket affixed to it in slidable engagement. The clamp means on the bracket includes two jaws each engaging top and bottom edges of the support arm respectively, the clamp means including a movable jaw which pivots on a lever arm extending from the bracket such that the movable jaw forceably engages a bearing surface along one of the edges of the support arm. The bracket is slidably affixed to the support arm on only one side such that when the jaw is moved to a point of release, the jaws of the clamp means are laterally releasable from the edges of the support arm.
The low friction of the slide assembly of the present invention is beneficial in that it requires a lower actuator force which contributes to the lower power consumption, low noise, and longer life of the actuator motor and drive system which may be any suitable screw or gear-drive system known in the art. The invention achieves all of these attributes while rigidly restricting movement along all axes of motion except the longitudinal axis of the support arm. The rigidity of the system is further enhanced by employing guide rails which are vertically spaced a greater distance apart than other known internal slide assemblies. This provides wide-track stability in the vertical plane and thus torsional vibration is mitigated and stable reflected vision through the mirror plate is achieved. Other objects and advantages of the present invention will be apparent from the following drawings and description of the preferred embodiment.